1. Field of the Invention
The present invention relates to cooling gas turbine engine compartments by venting and, more particularly, to venting hot air from gas turbine engine compartments subject to soak back when the engine is shut down.
2. Description of Related Art
Aircraft gas turbine engines have many compartments associated with the engine that are subject to heating due to soak back. The engines typically include a fan, a low pressure compressor, a high pressure compressor, a combustor, a high pressure turbine, and a low pressure turbine. The high pressure compressor, combustor, and high pressure turbine are collectively referred to as a core engine. An engine nacelle system for the engine extends circumferentially about the engine, sheltering the engine and providing aerodynamic surfaces which cooperate with the turbofan engine for generating thrust. A typical engine nacelle system includes a fan compartment surrounding a fan case and a core nacelle surrounding the core engine. The core nacelle is radially spaced apart from the core engine and a core compartment extending around the core engine is located therebetween. The core nacelle is disposed radially inwardly of the fan compartment leaving a region therebetween for the fan air flowpath.
The core compartment houses various engine components and accessories. The components and accessories include aircraft and engine hydraulic system components with hydraulic fluid therein which is flowed to the aircraft and engine hydraulic systems. The hydraulic fluid begins to deteriorate above a certain temperature and the amount of deterioration is a function of the time that it remains at that temperature. The core compartment gets very hot during engine operation and the components and accessories therein may be adversely affected by overheating. The core compartment is typically ventilated during engine operation by cooling passages which flow a portion of cool pressurized air from the fan flowpath to the core compartment thus keeping the core compartment relatively cool during engine operation.
During engine shutdown and for a period of time after engine shutdown, sensible heat stored in the engine is transferred to air in the core compartment as well as the fan compartment. An electronic controller such as full authority digital electronic control (FADEC) may be stored in the fan compartment. The heat causes the temperature of the air to rise causing heating of components and accessories in the engine nacelles and especially components such as hydraulic conduits in the upper portion of the engine nacelle where the hottest nacelle air is gathered. There are engine designs such as the HF120 for the honda jet that place the engine controller in compartments in pylons supporting the engine. The pylon compartment, FADEC compartment, and core compartments are all examples of engine associated compartments that require cooling after engine shutdown to prevent soak back heat from overheating engine associated compartments.
Recently, some engines have been developed that require the FADEC to operate, thus generating heat (about 100 W), when the engine is shut down and no cooling is available for maintenance purposes. These compartments containing the FADEC require cooling after engine shutdown to prevent heat generated by the operating FADEC from building up in the compartment and overheating the FADEC.
Currently cooling is provided by passive systems that vent hot air in compartments through various vent holes and vent areas. It is highly desirable to provide a passive cooling system better able to cool engine associated compartments after engine shutdown to prevent soak back or sensible heat from overheating engine associated compartments.